An upper-level low pressure sliding down the British Columbia coastline brings a productive snow pattern for the west slopes of the Cascades and passes on Sunday.
With cold air aloft, expect vigorous rain and snow shower activity, including locally intense snowfall, isolated thunder snow, and graupel. Convergence continues to enhance snow totals in the southern mountain loop and Stevens Pass areas where another 6-12" of snow is possible in some areas. Snow shower activity tapers by 10 AM for the Mt Baker and Hurricane Ridge areas and then gradually decreases elsewhere from late morning onwards as the trough slides eastward and WNW flow turns more NNWerly. Before the wind shift, expect moderate ridgeline winds for the central and southern Cascades, particularly near and east of the Cascade Crest where strong gusts continue through the morning hours.
Snow showers taper to flurries in the evening hours on Sunday, lingering longest around Mt Hood. Expect partial clearing overnight with light winds and seasonable temperatures.
A ridge amplifies offshore on Monday, bringing our region a mostly sunny day. Freezing levels start below the passes, but bump up to 3500-4500 ft in the afternoon for Washington State and up to 7000 ft for Mt Hood.
Weather Forecast
Olympics
West North
West Central
West South
Stevens Pass
Snoqualmie Pass
East North
East Central
East South
Mt. Hood
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Sunday
Moderate rain and snow showers quickly taper in the morning hours and become light with sun breaks in the afternoon.
Sunday
Night
Partly cloudy.
Sunday
Moderate rain and snow showers quickly taper in the morning hours and become light with sun breaks in the afternoon.
Sunday
Night
Partly cloudy.
Sunday
Heavy rain, snow, and graupel showers and convergence in the morning (southern part), moderate (northern part). Shower activity becomes mostly light by the afternoon.
Sunday
Night
Flurries and sprinkles in the evening, then gradually decreasing clouds overnight.
Sunday
Heavy rain and snow showers at Paradise, decreasing to moderate in the afternoon; moderate rain and snow showers for Crystal and White Passes, becoming light in the afternoon. Moderate ridgeline winds become light.
Sunday
Night
Flurries and sprinkles in the evening, then gradually decreasing clouds overnight.
Sunday
Heavy rain and snow showers decrease into the light to moderate range by the afternoon. Moderate ridgeline winds become light. Decreasing light W wind at the Pass.
Sunday
Night
Flurries and sprinkles in the evening, then gradually decreasing clouds overnight. Light ridgeline and W wind at the Pass.
Sunday
Moderate to heavy rain and snow showers decrease into the light range by the afternoon. Moderate ridgeline winds become light late in the day. Decreasing light W wind at the Pass.
Sunday
Night
Flurries and sprinkles in the evening, then gradually decreasing clouds overnight. Light ridgeline and W wind at the Pass.
Sunday
Decreasing light snow showers. Decreasing light to moderate ridgeline winds.
Sunday
Night
Mostly clearing skies. Light ridgeline winds.
Sunday
Moderate snow showers near the Cascade Crest in the morning, then tapering to flurries. Light snow showers further east ending by mid-morning. Decreasing moderate ridgeline winds.
Sunday
Night
Partly cloudy in the evening, then clearing skies overnight.
Sunday
Moderate snow showers near the Cascade Crest in the morning, then tapering to flurries. Light snow showers further east ending by mid-morning. Decreasing moderate ridgeline winds.
Sunday
Night
Partly cloudy in the evening, then clearing skies overnight.
Sunday
Heavy rain and snow showers decrease into the moderate range by the afternoon. Decreasing moderate ridgeline winds.
Sunday
Night
Light snow showers end overnight. Decreasing light ridgeline winds.
The NWAC program is administered by the USDA-Forest Service and operates from the National Weather Service Forecast Office in Seattle. NWAC services are made possible by important collaboration and support from a wide variety of federal, state and private cooperators.
The 5000’ temperature forecast does not imply a trend over the 12 hr period and only represents the max and min temperatures within a 12 hr period in the zone. The 6-hr snow level forecast, the forecast discussion, and weather forecast sections may add detail regarding temperature trends.
The snow level forecast represents the general snow level over a 6 hr time period. Freezing levels are forecast when precipitation is not expected.
*Easterly or offshore flow is highlighted with an asterisk when we expect relatively cool east winds in the major Cascade Passes. Easterly flow will often lead to temperature inversions and is a key variable for forecasting precipitation type in the Cascade Passes. Strong easterly flow events can affect terrain on a more regional scale.
Ridgeline winds are the average wind speed and direction over a 6 hr time period.
The wind forecast represents an elevation range instead of a single elevation slice. The elevation range overlaps with the near and above treeline elevation bands in the avalanche forecast and differs per zone.
Wind direction indicates the direction the wind originates or comes from on the 16-point compass rose.
Water Equivalent (WE) is the liquid water equivalent of all precipitation types; rain, snow, ice pellets, etc., forecast to the hundredth of an inch at specific locations. To use WE as a proxy for snowfall amounts, start with a snow to water ratio of 10:1 (10 inches of snow = 1 inch WE). Temperatures at or near freezing will generally have a lower ratio (heavy wet snow) and very cold temperatures can have a much higher ratio (dry fluffy snow).